Nubo wrote:Filling the case with fluid is an interesting concept. The first (really big) question is whether there's a fluid that could safely be introduced into the pack long-term. Second question is how much such a fluid would cost, and then there is weight. Finally, how fluid-tight is the case once it's filled with many pounds of liquid and subjected to G-forces.
Assuming all these work out, it probably help to conduct heat from the cell internals to the metal case (much better than air), where you could then extract it fairly easily in a number of ways.
Take from those using liquid cooling for computer boards, it sounds cool but is not practical. First you need a liquid that is an electrical insulator (for obvious reasons electric car), and then you want something that won't corrode or mess up any internal wiring, battery, etc. The problem is, just about anything liquid is going to have some weird reaction with metal. Air just works better as being the least reactive. Add in what has mentioned, extra weight, sloshing, leaking, etc. It would be better to just vent filtered air through the battery pack given all it would take create the desired effect using liquid.